Extra-Dimensional Processes
Scenarios with extra dimensions (ED) allow a multitude of processes.
Currently three different categories of processes are implemented.
The first involves the production of excited Kaluza Klein states
within so-called Randall-Sundrum (RS) scenarios, the second is
related to resonance production in TeV-1 sized extra dimensions
and the third relates to phenomena from large extra dimensions (LED).
Due to the close relation between the LED model and a so-called
unparticle model, similar unparticle processes are also kept in this
section.
Randall-Sundrum Resonances, production processes
The graviton (G*) and gluon (KKgluon*) resonance states are assigned
PDG code 5100039 and 5100021 respectively. The G* processes are
described in [Bij01] and the KKgluon* process in [Ask11].
Decays into fermion and boson pairs are handled with the correct
angular distributions, while subsequent decays are handled
isotropically.
There are two lowest-order processes that together normally
should be sufficient for a simulation of G^* production.
flag ExtraDimensionsG*:all
(default = off)
Common switch for the group of lowest-order G^* production
processes, i.e. the two ones below.
flag ExtraDimensionsG*:gg2G*
(default = off)
Scatterings g g → G^*.
Code 5001.
flag ExtraDimensionsG*:ffbar2G*
(default = off)
Scatterings f fbar → G^*.
Code 5002.
In addition there are three first-order processes included. These
are of less interest, but can be used for dedicated studies of the
high-pT tail of G^* production. As usual, it would
be double counting to include the lowest-order and first-order
processes simultaneously. Therefore the latter ones are not included
with the ExtraDimensionsG*:all = on option. In this set
of processes all decay angles are assumed isotropic.
flag ExtraDimensionsG*:gg2G*g
(default = off)
Scatterings g g → G^* g.
Code 5003.
flag ExtraDimensionsG*:qg2G*q
(default = off)
Scatterings q g → G^* q.
Code 5004.
flag ExtraDimensionsG*:qqbar2G*g
(default = off)
Scatterings q qbar → G^* g.
Code 5005.
There is also one process for the production of a gluon resonance.
flag ExtraDimensionsG*:qqbar2KKgluon*
(default = off)
Scatterings q qbar → g^*/KKgluon^*.
Code 5006.
Randall-Sundrum Resonances, parameters
In the above scenario the main free parameters are the masses, which
are set as usual. In addition there are the following coupling parameters.
The coupling kappaMG follows the conventions in [Bij01],
where as the flavour dependent couplings follow the conventions used in
[Dav01].
flag ExtraDimensionsG*:SMinBulk
(default = off)
Parameter to choose between the two scenarios:
off, SM on the TeV brane (common kappaMG coupling);
on, SM in the ED bulk (flavour dependent couplings).
This parameter is only relevant for the lowest-order graviton
(G*) processes, where as the first-order processes
corresponds to the off scenario.
flag ExtraDimensionsG*:VLVL
(default = on)
Parameter to specify Z/W coupling scenario:
off, usual Z/W boson couplings;
on, coupling only to longitudinal Z/W bosons.
In both cases the GZZ and GWW values are used
and this parameter is only relevant when SMinBulk = on.
The formulas for longitudinal bosons should be appropriate up to
O(m_V/E_V) corrections.
parm ExtraDimensionsG*:kappaMG
(default = 0.054; minimum = 0.0)
dimensionless coupling, which enters quadratically in all on-shell
partial widths of the G^*. Is
kappa m_G* = sqrt(2) x_1 k / Mbar_Pl,
where x_1 = 3.83 is the first zero of the J_1 Bessel
function and Mbar_Pl is the modified Planck mass.
In width and cross section calculations, kappa is fixed by
the on-shell G^* mass and kappaMG, i.e.
kappaMG scales with the off-shell G^* mass.
parm ExtraDimensionsG*:Gll
(default = 0.0; minimum = 0.0)
Coupling between graviton and leptons.
parm ExtraDimensionsG*:Gqq
(default = 0.0; minimum = 0.0)
Coupling between graviton and light quarks.
parm ExtraDimensionsG*:Gbb
(default = 0.0; minimum = 0.0)
Coupling between graviton and bottom quark.
parm ExtraDimensionsG*:Gtt
(default = 0.001; minimum = 0.0)
Coupling between graviton and top quark.
parm ExtraDimensionsG*:Ggg
(default = 0.000013; minimum = 0.0)
Coupling between graviton and gluon.
parm ExtraDimensionsG*:Ggmgm
(default = 0.000013; minimum = 0.0)
Coupling between graviton and gamma.
parm ExtraDimensionsG*:GZZ
(default = 0.001; minimum = 0.0)
Coupling between graviton and Z boson.
parm ExtraDimensionsG*:GWW
(default = 0.001; minimum = 0.0)
Coupling between graviton and W boson.
parm ExtraDimensionsG*:Ghh
(default = 0.001; minimum = 0.0)
Coupling between graviton and Higgs bosons.
parm ExtraDimensionsG*:KKgqR
(default = -0.2)
Coupling between KK-gluon and a right-handed light quark.
parm ExtraDimensionsG*:KKgqL
(default = -0.2)
Coupling between KK-gluon and a left-handed light quark.
parm ExtraDimensionsG*:KKgbR
(default = -0.2)
Coupling between KK-gluon and a right-handed bottom quark.
parm ExtraDimensionsG*:KKgbL
(default = 1.0)
Coupling between KK-gluon and a left-handed bottom quark.
parm ExtraDimensionsG*:KKgtR
(default = 4.0)
Coupling between KK-gluon and a right-handed top quark.
parm ExtraDimensionsG*:KKgtL
(default = 1.0)
Coupling between KK-gluon and a left-handed top quark.
mode ExtraDimensionsG*:KKintMode
(default = 0; minimum = 0; maximum = 2)
Choice of full g^*/KK-gluon^* structure or not in relevant
processes.
option 0 : full g^*/KK-gluon^* structure, with
interference included.
option 1 : only pure gluon_{SM} contribution.
option 2 : only pure gluon_{KK} contribution.
TeV^-1 Sized Extra Dimension, production processes
This section contains a processes involving the production
of electroweak KK gauge bosons, i.e. gamma_{KK}/Z_{KK},
in one TeV^-1 sized extra dimension. The process is described
in [Bel10] and allows for individual final states to be
specified.
flag ExtraDimensionsTEV:ffbar2ddbar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → d dbar ,
Code 5061.
flag ExtraDimensionsTEV:ffbar2uubar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → u ubar ,
Code 5062.
flag ExtraDimensionsTEV:ffbar2ssbar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → s sbar ,
Code 5063.
flag ExtraDimensionsTEV:ffbar2ccbar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → c cbar ,
Code 5064.
flag ExtraDimensionsTEV:ffbar2bbbar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → b bbar ,
Code 5065.
flag ExtraDimensionsTEV:ffbar2ttbar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → t tbar ,
Code 5066.
flag ExtraDimensionsTEV:ffbar2e+e-
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → e+ e- ,
Code 5071.
flag ExtraDimensionsTEV:ffbar2nuenuebar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → nue nuebar ,
Code 5072.
flag ExtraDimensionsTEV:ffbar2mu+mu-
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → mu+ mu- ,
Code 5073.
flag ExtraDimensionsTEV:ffbar2numunumubar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → numu numubar ,
Code 5074.
flag ExtraDimensionsTEV:ffbar2tau+tau-
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → tau+ tau- ,
Code 5075.
flag ExtraDimensionsTEV:ffbar2nutaunutaubar
(default = off)
Scatterings f fbar → (gamma_{KK}/Z_{KK}) → nutau nutaubar ,
Code 5076.
TeV^-1 Sized Extra Dimension, parameters
Irrespective of the parameter options used, the particle produced,
gamma_{KK}/Z_{KK}, will always be assigned code 5000023.
mode ExtraDimensionsTEV:gmZmode
(default = 3; minimum = 0; maximum = 5)
Choice of full gamma_{KK}/Z_{KK} structure or not in relevant
processes.
option 0 : full gamma_{SM}/Z_{SM} structure, with
interference included.
option 1 : only pure gamma_{SM} contribution.
option 2 : only pure Z_{SM} contribution.
option 3 : full gamma_{KK}/Z_{KK} structure, with
interference included.
option 4 : only pure gamma_{KK} contribution, with
SM interference included.
option 5 : only pure Z_{KK} contribution, with SM
interference included.
mode ExtraDimensionsTEV:nMax
(default = 10; minimum = 1; maximum = 100)
The number of included KK excitations.
parm ExtraDimensionsTEV:mStar
(default = 4000.0; minimum = 1000.0)
The KK mass m^*, given by the inverse of the single extra
dimension radius.
Large Extra Dimensions, production processes
The LED graviton, where the KK-modes normally are summed and do not
give rise to phenomena individually, is assigned PDG code 5000039.
The graviton emission and virtual graviton exchange processes use
the same implementation as the corresponding unparticle processes,
which are all described in [Ask10]. It is also possible to
generate monojet events from scalar graviton emission as described
in [Azu05], by turning on the option GravScalar.
Note: As discussed in [Ask09], for the graviton or
unparticle emission processes the underlying Breit-Wigner mass
distribution should be matched to the graviton mass spectrum in order
to achieve an optimal MC efficiency.
The following lowest order graviton emission processes are available.
flag ExtraDimensionsLED:monojet
(default = off)
Common switch for the group of lowest-order G jet emission
processes, i.e. the three ones below.
flag ExtraDimensionsLED:gg2Gg
(default = off)
Scatterings g g → G g.
Code 5021.
flag ExtraDimensionsLED:qg2Gq
(default = off)
Scatterings q g → G q.
Code 5022.
flag ExtraDimensionsLED:qqbar2Gg
(default = off)
Scatterings q qbar → G g.
Code 5023.
flag ExtraDimensionsLED:ffbar2GZ
(default = off)
Scatterings f fbar → G Z.
Code 5024.
flag ExtraDimensionsLED:ffbar2Ggamma
(default = off)
Scatterings f fbar → G gamma. This process corresponds
to the photon limit of the G Z process, as described in
[Ask09].
Code 5025.
The following LED processes with virtual graviton exchange are
available.
flag ExtraDimensionsLED:ffbar2gammagamma
(default = off)
Scatterings f fbar → (LED G*) → gamma gamma. If the
graviton contribution is zero, the results corresponds to the
SM contribution, i.e. equivalent to
PromptPhoton:ffbar2gammagamma.
Code 5026.
flag ExtraDimensionsLED:gg2gammagamma
(default = off)
Scatterings g g → (LED G*) → gamma gamma.
Code 5027.
flag ExtraDimensionsLED:ffbar2llbar
(default = off)
Scatterings f fbar → (LED G*) → l l , where
l is a charged lepton. If the graviton contribution
is zero, the results corresponds to the SM contribution, i.e.
similar to WeakSingleBoson:ffbar2gmZ. Does not
include t-channel amplitude relevant for e^+e^- to e^+e^-
and no K-factor is used.
Code 5028.
flag ExtraDimensionsLED:gg2llbar
(default = off)
Scatterings g g → (LED G*) → l l.
Code 5029.
Dijet production including graviton exchange is also available, using
the same effective theory approach as the LED G exchange processes
above or including more detailed amplitudes in accordance with
[Fra11]. In case of the latter, the value of LambdaT
is used as the value of the cut-off scale Lambda. For this
reason the dijet processes only relates to the LED model and no
unparticle versions are available. The processes are grouped together
like their HardQCD equivalents and should therefore converge
to the same results in the limit of an insignificant graviton
contribution.
Warning: These LED dijets processes are still being validated.
flag ExtraDimensionsLED:dijets
(default = off)
Common switch for the group of lowest-order jet jet
production processes with graviton exchange, i.e. the six ones
below.
flag ExtraDimensionsLED:gg2DJgg
(default = off)
Scatterings g g → (LED G*) → g g.
Code 5030.
flag ExtraDimensionsLED:gg2DJqqbar
(default = off)
Scatterings g g → (LED G*) → q qbar. Number of
outgoing flavours specified by nQuarkNew parameter
below.
Code 5031.
flag ExtraDimensionsLED:qg2DJqg
(default = off)
Scatterings q g → (LED G*) → q g and
qbar g → (LED G*) → qbar g.
Code 5032.
flag ExtraDimensionsLED:qq2DJqq
(default = off)
Scatterings q q(bar)' → (LED G*) → q q(bar)'.
Including q and qbar of same or different
flavours, but the outgoing flavours equals the incoming ones.
Code 5033.
flag ExtraDimensionsLED:qqbar2DJgg
(default = off)
Scatterings q qbar → (LED G*) → g g.
Code 5034.
flag ExtraDimensionsLED:qqbar2DJqqbarNew
(default = off)
Scatterings q qbar → (LED G*) → q' qbar'. Number of
outgoing flavours specified by nQuarkNew parameter below.
Code 5035.
Large Extra Dimensions, parameters
flag ExtraDimensionsLED:GravScalar
(default = off)
Allow the monojet processes to produce scalar graviton emission
instead of the default tensor one. The scalar option is according
to the processes described in [Azu05] and includes two
coupling constants below.
mode ExtraDimensionsLED:n
(default = 2; minimum = 1)
Number of extra dimensions.
parm ExtraDimensionsLED:MD
(default = 2000.; minimum = 100.0)
Fundamental scale of gravity in D = 4 + n dimensions.
parm ExtraDimensionsLED:LambdaT
(default = 2000.; minimum = 100.0)
Ultraviolet cutoff parameter for the virtual graviton exchange processes.
mode ExtraDimensionsLED:NegInt
(default = 0; minimum = 0; maximum = 1)
Allows to change sign of the interference terms in the graviton exchange
processes, common in connection to using the Hewett convention
[Hew99].
option 0 : 1
option 1 : -1
mode ExtraDimensionsLED:CutOffMode
(default = 0; minimum = 0; maximum = 3)
Options for when the hard scale of the process (e.g. sHat)
approaches or exceed the scale of validity of the low energy effective
theory (e.g. M_D). Note: Option 1 only concerns the
graviton emission processes and the form factor is currently not available
for the scalar graviton processes.
option 0 : Do nothing, i.e. all values of sHat contribute.
option 1 : Truncate contributing sHat region
([Ask09]).
option 2 : Form factor, using mu = renormScale2 .
option 3 : Form factor, using mu = E_jet.
parm ExtraDimensionsLED:t
(default = 1.; minimum = 0.001)
Form factor parameter.
parm ExtraDimensionsLED:g
(default = 1.0; minimum = 0.0)
Coupling related to scalar graviton emission.
parm ExtraDimensionsLED:c
(default = 1.0; minimum = 0.0)
Coupling related to scalar graviton emission.
mode ExtraDimensionsLED:nQuarkNew
(default = 3; minimum = 0; maximum = 5)
Number of allowed outgoing new quark flavours in the above
q qbar → (LED G*) → q' qbar' and
g g → (LED G*) → q' qbar'
processes. Similar to HardQCD:nQuarkNew for the QCD processes.
mode ExtraDimensionsLED:opMode
(default = 0; minimum = 0; maximum = 1)
Options to specify S function for LED dijet amplitudes.
option 0 : Use detailed amplitude, as described in [Fra11].
option 1 : Use conventional LambdaT parametrization,
like the other LED processes.
Unparticles, production processes
As mentioned above, the similar unparticle and graviton processes
share the same implementations. The unparticle processes, however,
only use the dedicated unparticle parameters below. The unparticle
is also assigned the PDG code 5000039 and is therefore called
Graviton in the event record. The graviton and unparticle
emission as well as virtual graviton and unparticle exchange processes
are described in [Ask10].
Note: As discussed in [Ask09], for the graviton or
unparticle emission processes the underlying Breit-Wigner mass
distribution should be matched to the graviton mass spectrum in order
to achieve an optimal MC efficiency.
The following unparticle emission processes are available.
flag ExtraDimensionsUnpart:monojet
(default = off)
Common switch for the group of lowest-order U jet emission
processes, i.e. the three ones below.
flag ExtraDimensionsUnpart:gg2Ug
(default = off)
Scatterings g g → U g.
Code 5045.
flag ExtraDimensionsUnpart:qg2Uq
(default = off)
Scatterings q g → U q.
Code 5046.
flag ExtraDimensionsUnpart:qqbar2Ug
(default = off)
Scatterings q qbar → U g.
Code 5047.
flag ExtraDimensionsUnpart:ffbar2UZ
(default = off)
Scatterings f fbar → U Z.
Code 5041.
flag ExtraDimensionsUnpart:ffbar2Ugamma
(default = off)
Scatterings f fbar → U gamma. This process corresponds
to the photon limit of the U Z process, as described in
[Ask09].
Code 5042.
The following processes with virtual unparticle exchange are available.
flag ExtraDimensionsUnpart:ffbar2gammagamma
(default = off)
Scatterings f fbar → (U*) → gamma gamma. If the unparticle
contribution is zero in the spin-2 case, the results corresponds to
the SM contribution, i.e. equivalent to
PromptPhoton:ffbar2gammagamma.
Code 5043.
flag ExtraDimensionsUnpart:gg2gammagamma
(default = off)
Scatterings g g → (U*) → gamma gamma.
Code 5044.
flag ExtraDimensionsUnpart:ffbar2llbar
(default = off)
Scatterings f fbar → (U*) → l lbar , where
l is a charged lepton. If the unparticle contribution
is zero, the results corresponds to the SM contribution, i.e.
similar to WeakSingleBoson:ffbar2gmZ. Does not
include t-channel amplitude relevant for e^+e^- to e^+e^-
and no K-factor is used.
Code 5048.
flag ExtraDimensionsUnpart:gg2llbar
(default = off)
Scatterings g g → (U*) → l lbar.
Code 5049.
Unparticles, parameters
mode ExtraDimensionsUnpart:spinU
(default = 2; minimum = 0; maximum = 2)
Unparticle spin.
parm ExtraDimensionsUnpart:dU
(default = 1.4; minimum = 1.0)
Scale dimension parameter.
parm ExtraDimensionsUnpart:LambdaU
(default = 2000.; minimum = 100.0)
Unparticle renormalization scale.
parm ExtraDimensionsUnpart:lambda
(default = 1.0; minimum = 0.0)
Unparticle coupling to the SM fields.
parm ExtraDimensionsUnpart:ratio
(default = 1.0; minimum = 1.0; maximum = 1.0)
Ratio, lambda'/lambda, between the two possible coupling constants
of the spin-2 ME. Warning: A ratio value different from one
give rise to an IR divergence which makes the event generation very slow, so
this values is fixed to ratio = 1 for the moment.
mode ExtraDimensionsUnpart:CutOffMode
(default = 0; minimum = 0; maximum = 1)
Options for when the hard scale of the process (e.g. sHat)
approaches or exceed the scale of validity of the low energy effective
theory (Lambda_U). This mode only concerns the unparticle
emission processes.
option 0 : Do nothing, i.e. all values of sHat
contribute.
option 1 : Truncate contributing sHat region
([Ask09]).
mode ExtraDimensionsUnpart:gXX
(default = 0; minimum = 0; maximum = 2)
Chiral unparticle couplings, gXX = gLL = gRR. Only relevant
for lepton production from spin-1 unparticle exchange.
option 0 : 1
option 1 : -1
option 2 : 0
mode ExtraDimensionsUnpart:gXY
(default = 0; minimum = 0; maximum = 2)
Chiral unparticle couplings, gXY = gLR = gRL. Only relevant
for lepton production from spin-1 unparticle exchange.
option 0 : 1
option 1 : -1
option 2 : 0